Command autocomplete does not work

A player presses Tab and nothing gets completed — a small thing that annoys constantly.

Causes

1. Permissions. Players can't see commands they don't have permission for — that's correct behavior — Permissions not applying.
2. Core configuration:

settings:
  tab-complete: 0

in spigot.yml. A value of -1 disables tab completion entirely, 0 enables it.

1. A security plugin that hides commands from players (anti-plugin-discovery). Some of these plugins break tab completion completely.
2. Proxy: backend commands may not reach tab completion on the proxy — Velocity.
3. Client: older versions connecting through ViaVersion sometimes lose tab completion — Via.

Nicknames

Nickname completion always works as long as the player can see others: if it doesn't, check your vanish plugin and entity tracking.

Why it matters

Tab completion is part of usability, especially for Bedrock players, who find typing text hard — Commands on mobile.